In a gas turbine or a turbo refrigerator, an axial-flow compressor, which is one type of axial-flow fluid machinery, is used to compress a gas. This type of axial-flow fluid machine includes a plurality of variable vanes disposed around a rotor in an annular shape, and a variable vane drive device configured to change directions of the variable vanes.
For example, as disclosed in the following Patent Document 1, a variable vane drive device includes a movable ring, a ring support unit, an actuator, and a link unit. The movable ring is disposed at an outer circumferential side of a vane support ring (a casing) and has an annular shape. The ring support unit rotatably supports the movable ring. The actuator rotates the movable ring. The link unit connects the movable ring to the plurality of variable vanes. The ring support unit has two first rollers and one second roller. The first rollers are disposed at an outer circumferential side of the movable ring, which is the lower side of the vane support ring, at an interval in a circumferential direction of the movable ring. The second roller is disposed at an inner circumferential side of the movable ring, which is the lower side of the vane support ring, at an interval from the two first rotors in the circumferential direction of the movable ring.
The two first rollers support the movable ring from a lower side thereof, and restrict downward movement of the movable ring. The one second roller is pressed downward by a spring, and presses the movable ring downward. That is, the second roller presses the movable ring in a direction in which the movable ring approaches the first rollers, and secures a contact pressure between the movable ring and the first rollers.
In the axial-flow compressor, a pressure of a gas gradually increases as it flows to the downstream side, and a temperature of the gas increases. For this reason, a temperature difference is generated between an inside and an outside of the vane support ring during a startup process and a shutdown process of the axial-flow compressor, and a thermal expansion difference is generated between the vane support ring and the movable ring disposed at the outer circumferential side of the vane support ring. For this reason, in the variable vane drive device disclosed in Patent Document 1, only a lower portion of the movable ring is supported by the first rollers and the second roller. In addition, with an upper side of the movable ring being in a free state, even when the movable ring thermally expands to relatively increase a diameter of the movable ring with respect to a diameter of the vane support ring, an upper portion of the movable ring can move upward.